Recently, cancer treatment has seen notable progress. Especially, the success rate of cure of a primary cancer by surgery or radiotherapy has been improved, thereby contributing greatly to the progress in cancer treatment. Screening of metastatic cancers is important in cancer treatment. Non-metastatic cancers are usually respectable, while metastatic cancers are usually unrespectable. The non-metastatic tumors are usually treated by surgical elimination. For patients with cancer that has spread or metastasised, radiation, chemotherapy, or a combination of chemotherapy and radiation can be offered as treatment. Therefore, method and kit that can diagnosis whether a cancer is metastatic would be helpful for determining the most effective way to treat the cancer. Serological cancer metastatic markers are useful for screening, determining diagnoses and prognoses, assessing responses to therapy, and monitoring for cancer recurrence, and thus are highly beneficial in diagnosing and treating cancers (Basuyau et al., 2001; Thomas and Sweep, 2001; Petricoin et al., 2006; Brenner et al., 2007; Rodrigues et al., 2007; Shields et al., 2007; Skates et al., 2007; Wang et al., 2007; Zhang and Chan, 2007).
Metastasis of cancer involves a multi-step process, including the ability of cancer cells to escape from their original position, degrade the extracellular matrix (ECM), and migrate through ECM (Bogenrieder and Herlyn, 2003). Currently, the mechanism of cancer metastasis is presumed to be as follows. (1) Cancer cells proliferate in a primary cancer colony; (2) new blood vessels are newly formed; (3) the malignant cancer cells infiltrate and penetrate the newly formed blood vessels; (4) the cancer cells circulate within the human body; (5) the cancer cells reach a target organ; (6) the cancer cells extravasate from blood vessels; (7) the cancer cells proliferate in the target organ; and (8) a metastatic focus is formed.
Metastatic cancer cells can secrete extracellular matrix (ECM)-degradation protease to degrade ECM during metastasis. MMPs (matrix metalloproteinases) are enzymes involved in the degradation of ECM (Nguyen et al., 1998; Holmbeck et al., 2004; Lee et al., 2007). MMP-2 plays a major role in ECM degradation during cancer metastasis (Stetler-Stevenson et al., 1993). Experiment showed that MMPs production could be regulated at the level of secretion (Taraboletti et al., 2000). Thus, the metastatic cancer cells may develop strong secretory ability to enhance MMPs secretion and thereby enhancing their metastasis abilities (Moser et al., 1994; Jena, 2005).
The cellular apoptosis susceptibility (CAS, or CSE1L/CAS) protein (GenBank accession no. U33286) was identified in a study of an antisense DNA fragment that is capable of causing cell resistance to apoptosis induced by Pseudomonas exotoxin, diphtheria toxin, and tumor necrosis factors (Brinkmann et al., 1995a). CAS protein also regulates apoptosis induced by cypermethrin (Izaguirre et al., 2006), interferon-γ (Jiang et al., 2007), and chemotherapeutic drugs (Liao et al., 2008a; Liao et al., 2008b). The CAS gene is the human homologue of the yeast chromosome segregation gene, CSE1 (Brinkmann et al., 1995b). As CAS protein is able to associate with microtubules (Scherf et al., 1996) and importin-α, a nuclear-transport receptor (Kutay et al., 1997), CAS is mainly distributed in the nuclei and cytoplasm surrounding perinuclear areas of cells. Pathological studies showed that the expression of CAS protein was correlated positively with high cancer stage and high cancer grade as well as worse outcome of the cancer patients (Wellmann et al., 1997; Boni et al., 1999; Behrens et al., 2001; Peiro et al., 2001; Wellmann et al., 2001; Behrens et al., 2003; Seiden-Long et al., 2006).
U.S. Pat. No. 6,664,057 pertains to the identification of a novel amplicon on human chromosome 20q13.2 which is associated with cancer. U.S. Pat. No. 6,072,031 provides the cDNA and amino acid sequences for the cellular apoptosis susceptibility (CAS) protein are used to detect expression and amplification of the CAS gene in normal and cancer cells. An antisense CAS gene sequence introduced into living cells inhibits CAS protein activity and thus prevents or inhibits apoptosis in the cells. U.S. Pat. No. 5,759,782 provides the cDNA and amino acid sequences for the cellular apoptosis susceptibility (CAS) protein are used to detect expression and amplification of the CAS gene in normal and cancer cells. An antisense CAS gene sequence introduced into living cells inhibits CAS protein activity and thus prevents or inhibits apoptosis in the cells. U.S. Pat. No. 6,440,737 provides antisense compounds, compositions and methods for modulating the expression of CAS gene. U.S. Pat. No. 6,232,086 discloses the cDNA and amino acid sequences for a CAS protein that can be used to detect expression and amplification of the CAS gene in normal and cancer cells. U.S. Pat. No. 6,156,564 pertains to a method of detecting human proliferating cells comprising measuring a level of a human CAS protein in a human cell sample and detecting the human CAS protein at a level at least two times greater than the level of a human CAS protein in normal nonproliferating human cells. U.S. Pat. No. 6,207,380 provides polypeptides and polynucleotides useful for detecting, diagnosing, staging, monitoring, prognosticating, in vivo imaging, preventing or treating, or determining the predisposition of an individual to diseases and conditions of the urinary tract, such as urinary cancer, are described. These sequences are derived from keratin/cytokeratin, CAS, or mat-8 polypeptides and polynucleotides. U.S. Pat. No. 6,207,380 also provided are antibodies that specifically bind to keratin/cytokeratin, CAS, or mat-8-encoded polypeptides or proteins, which molecules are useful for the therapeutic treatment of urinary tract diseases, tumors or metastases. Thus, U.S. Pat. No. 6,207,380 describes using antibodies that specifically bind to keratin/cytokeratin, CAS, or mat-8 for the therapy of urinary tract diseases, tumors or metastases. The prior art above detect the expression of CAS gene in cell level. Therefore, according to the contents and claims described in these prior arts, non of these arts describe or claim measuring CAS level in the body fluids from a mammal for the screening or diagnosis of cancer metastasis.
Metastasis still remains the main cause of death for most cancer patients. Metastasis is the major characteristic of high-stage cancer and the major cause of cancer death. The obstacle to successful treatment of cancer continues to be the lack of sound markers that can screen metastatic cancers accurately. In colorectal cancers, they are one of the most common leading causes of cancer-related deaths in the world. Non-metastatic colorectal cancers are resectable, and the 5-year survival percentage can exceed 90%, whereas metastatic colorectal cancers are usually unresectable, and the 5-year survival percentage may be only about 5% (Breslow et al., 1997; Rex et al., 2006). Thus, a reliable serological marker would be helpful for screening metastatic colorectal cancers and would be beneficial for colorectal cancer treatment (Bresalier et al., 2004; Stein et al., 2006; Lassmann et al., 2007; Gupta et al., 2008; Ransohoff et al., 2008). The carcinoembryonic antigen (CEA), a heavily glycosylated protein associated with the progression of colorectal tumors, is the tumor marker most frequently used in assessing the prognosis of colorectal cancers (Gold and Freedman, 1965; Hammarström, 1999). By using a radio-immunoassay method, Thomson et al. reported that circulating CEA was positive in 97% of patients with colorectal cancer (Thomson et al. 1969). Nevertheless, the high blood CEA in bowel cancers apparently have a relevance with patients had advanced disease with extensive metastases, especially liver involvement (Moertel et al. 1993). Also, many studies have reported that elevation of CEA level in blood is not necessarily correlated well with the presence of metastasis of colon or rectal cancers (Hsu T C 2006; Saito et al., 2005); patients with benign colorectal diseases may also show raised serum CEA levels (Fong et al., 1985). Thus, the main clinical utility of CEA is in monitoring colorectal carcinoma after surgical resection, when increased values suggest recurrence and consistently normal values suggest the absence of recurrence (Go, 1976; Savrin et al., 1979; Chu et al., 1991). Therefore, there is still a need for more reliable cancer markers that can diagnose cancer metastasis more accurately, which in turn will be of great help to the diagnosis and prognosis of cancers as well as cancer treatment. Due to the difficulties in the current approaches to the diagnosis of cancer metastases, there is a need in the art for improved methods and kits for diagnosing cancer metastasis.